Lens barrel and image pickup apparatus

A lens barrel having a first lens, a second lens, a lens holding unit adapted to hold the second lens in such a manner that the second lens moves relatively closer to or apart from the first lens in an optical axis direction of the lens barrel, and an iris diaphragm arranged between the first lens and the second lens and having diaphragm blades to adjust an amount of incident light, the lens barrel moving between a photographing position and a stored position in the optical axis direction to change the photographing magnification, wherein

• the second lens includes a convex spherical portion, protruding toward the first lens, at an end face thereof facing the first lens in the optical axis direction, and
• the second lens is arranged close to the first lens and an inner circumferential portion of the diaphragm blades is arranged inwardly in the radial direction with respect to the lens holding unit and oppositely to the convex spherical portion in the radial direction, when the lens barrel is in the stored position.